This application claims the benefit of U.S. Patent Application Serial No. 60/191,221, filed Mar. 22, 2000.
1. Field of the Invention
This invention relates generally to automobile bumpers, and in particular to an improved method for making a vehicular bumper assembly having a fascia with an integral energy absorber.
2. Description of the Related Art
Automobile bumpers typically comprise an impact beam or reinforcement beam, energy absorbers surrounding the impact beam, and a fascia surrounding the energy absorber. The impact beam is typically made of high strength steel or aluminum, attached to the vehicle frame, and effectively provides the impact strength of the bumper. The energy absorber is typically a foam material, although it can alternatively be a hydraulic or gas piston and cylinder assembly. The fascia is the visible exterior of the bumper, and is typically made of plastic.
Referring now to FIG. 1, a prior art bumper system is generally depicted comprising a vehicle 10 with an attached bumper assembly 12. The bumper assembly 12 comprises a bumper beam 20, an energy absorbing layer 22, and a fascia 24. The bumper beam 20 typically comprises a rigid metallic member and is rigidly attached to the frame of the vehicle 10 in a conventional manner. The fascia 24 is typically made of a polymeric material conforming to the color and styling of the vehicle 10. The energy absorbing layer 22 is sandwiched between the fascia 24 and the bumper beam 20. The fascia 24 and energy absorbing layer 22 are attached to the vehicle in a conventional manner, depicted generally in FIG. 1 as utilizing a series of fasteners 14.
Typically, the fascia is manufactured by a high-pressure plastic injection molding process. Current injection molding processes suitable for making the fascia, however, are incapable of molding a fascia which is less than 3 mm thick. It is desirable, however, to provide a fascia having a thickness of less than 3 mm. A reduced thickness would result in less plastic being used to manufacture the bumper, thereby reducing the cost. A reduced thickness would also reduce the weight of the bumper, providing increased fuel efficiency.
In the past, the fascia of bumpers has been painted by way of a spray painting process. This process creates a great deal of environmental concerns and results in the use of expensive equipment to capture the volatile-organic compounds used in the spray painting process. The spray painting process further has relatively high rejection rates due to dirt and other spray painting defects. These and other factors tend to make the spray painting process very costly.
The bumper components have typically been separately shipped to the assembly plant for incorporation into the vehicle. The separate manufacturing and shipping of these components requires expensive packaging to ensure that the components are not damaged during shipment. The separate shipping and manufacturing requires additional floor space at both the manufacturing facility and the assembly plant, and further increases the cost of production.
Bumper fascias that incorporate a foam energy absorbing material are typically manufactured by a two-stage process. The first stage involves forming the fascia. The second stage involves adding the foam material to the fascia piece. This manufacturing process requires additional handling of the pieces, additional tooling, and additional manufacturing time, all adding to the production cost of the piece.
It is desirable to have a reduced thickness fascia that is pre-colored and integrally formed with a foam energy absorber to reduce the weight of the bumper, simplify the manufacturing process, and reduce storage space requirements.
In one aspect, the present invention comprises a vehicle comprising a body having a bumper mounting portion thereon, a bumper beam mounted to the bumper mounting portion, a fascia mounted to the vehicle in overlying fashion to the bumper beam, and an energy absorber integrally formed with the fascia and disposed between the fascia and the bumper beam, whereby the fascia and energy absorber can be manufactured, assembled, installed and replaced as a unit. In one embodiment of this aspect of the invention, the fascia has a thickness generally less than 3 mm. In another embodiment, the fascia comprises at least two layers of different materials, in which an outer layer comprises a transparent top coat material with a Class A finished surface, and an inner layer is colored to have an appearance consistent with the color of the vehicle. In another embodiment, the layers further comprise a structural layer, wherein the inner layer is interposed between the outer layer and the structural layer, where the structural layer is made of a relatively inexpensive material compared to the cost of the outer and inner layers, the outer and inner layers are relatively thin compared to the thickness of the structural layer, and the structural layer has a thickness of about 1.5 to 2.0 mm and is formed from recycled materials. In yet another embodiment, the energy absorber is formed from beads of expanded polypropylene, and the energy absorber and fascia can be shipped as a unit due to the integral formation of the energy absorber and the fascia.
In another aspect, the present invention comprises a bumper comprising a bumper beam for mounting to a vehicle, a fascia for mounting to the vehicle in overlying fashion to the bumper beam, and an energy absorber integrally formed with the fascia and disposed between the fascia and the bumper beam, whereby the fascia and energy absorber can be manufactured, assembled, installed and replaced as a unit.
In yet another aspect, the present invention comprises a fascia assembly for a vehicular bumper comprising a fascia having an inner surface and an outer surface, the outer surface having an aesthetic appearance consistent with the styling of a preselected vehicle, and an energy absorber formed integrally with the inner surface of the fascia.
In yet another aspect, the present invention comprises a method of making a fascia assembly for a vehicular bumper in a mold, the fascia assembly comprising a fascia made of a thermoplastic laminate material and an energy absorber, the mold comprising a first mold half having an inner surface defining a cavity and a second mold half defining a core that is movable into the cavity, the core having an outer surface facing the cavity, wherein the mold halves are selectively movable with respect to one another between a retracted position whereby the mold halves have space defined between the two, and a forming position wherein the mold halves contact and the mold core is disposed within the cavity, the method comprising the steps of positioning the thermoplastic laminate material between the mold halves when the mold halves are in the retracted position, clamping the thermoplastic laminate material between the mold halves by moving the mold halves to the forming position, drawing the thermoplastic laminate material against the inner surface of the lower mold half to form the fascia for the vehicular bumper; and injecting a foam material into the cavity to form an energy absorber that is integral with the fascia. In one embodiment of this aspect of the invention, the step of drawing the thermoplastic laminate material against the inner surface of the lower mold half further comprises the step of forming a vacuum between the thermoplastic laminate material and the inner surface of the lower mold half. In another embodiment, the step of drawing the thermoplastic laminate material against the inner surface of the lower mold half further comprises the step of forming a vacuum between the thermoplastic laminate material and the mold core. In yet another embodiment, the step of drawing the thermoplastic laminate material against the inner surface of the lower mold half further comprises the step of introducing pressurized air between the mold core and the thermoplastic laminate material after the drawing of a vacuum therebetween. In yet another embodiment, the step of injecting foam material into the cavity comprises injecting foam beads into the cavity. In yet another embodiment, the method of forming an energy absorber that is integral with the fascia further comprises the step of melting the foam beads by injecting steam into the cavity. In yet another embodiment, the method of forming an energy absorber that is integral with the fascia further comprises the step of compressing the foam beads after they are melted. In yet another embodiment, the step of compressing the foam beads after they are melted further comprises the step of moving the mold core toward the cavity.